Assignment 7

Hand this assignment in at the beginning of class on Tuesday March 30th.

This very nice short assignment uses the same data as Assignment 4. To refresh your memory, there are three accepted methods for doing a particular risky surgical procedure. We want to know if they differ in their probability of success. Patients are randomly assigned to each of the three methods, surgery is performed, and we record whether the surgery was successful or not. In the data file, surgical methods are labelled 1, 2 and 3. Success=1 means the operation was a success.

Start with what you did in Assignment 4. That is, use logistic regression to test whether the three probabilities of success pi₁, pi₂ and pi₃ are all equal. That's your initial test, which yields p = 0.005664708.

Now, still using logistic regression, conduct union-intersection follow-ups to the initial test, employing the traditional alpha level of 0.05, which will limit the joint Type I Error rate to 0.05.

1. What critical value are you going to use? Get a number with R and circle it on your printout.
2. Conduct each pairwise comparison. Circle the three test statistics on your printout, and give your conclusion in one plain sentence. For comparison, the smallest of my three test statistics was equal to 0.237.
3. You want to test whether pi₂ = (pi₁ + pi₃)/2. Look at your watch. Work on the problem for 10 minutes, and then stop. Don't show your work. Instead, on the back of your printout, draw a picture of how this problem makes you feel.